One trick I use is copy my back-up file (encrypted) to my cell phone's
micro-SD.. In the event disaster struck, I would either be out of the
house with my cell phone, or grab a few belongings including said mobile
before I rushed outside. The problem with that is that it still has the
original vfat .. formatting, and whatever it is, it doesn't like 4G+
files either :-)

People think I'm crazy, but, when I leave the house, I always carry a
disc wallet that holds the last year's worth of weekly full backups on
DVD+R. (Well, I probably am crazy, but this isn't a sign of it.)

I also double the weekly backups every month, and I keep the monthly
second copy in a safe deposit box. I also rotate USB external drives
through that safe deposit box. This is only for the really important
data, though. Miscellaneous other stuff just resides on two systems and
an external drive.

(...)

Apart from the cost of the medium... I am very suspicious of all the
hidden stuff that infects anything Blu-Ray.. And you're probably right..
may turn out to be unsuitable for data archiving.